This study aimed to determine the effect of active warm-up by local muscle light exercise and passive warm-up by polarized light irradiation on skin and muscle temperatures and forearm muscle performance (muscle strength, power, endurance, and controlled force-exertion). Ten healthy males performed various grip tests before and after active (local muscle light exercise) and passive (linear polarized near-infrared light irradiation) warm-ups. An active warm-up involved intermittent gripping exercise (contraction: 1 second and relaxation: 1 second) for 10 minutes using a sponge. A passive warm-up consisted of polarized light irradiation to the forearm (superficial digital flexor) for 10 minutes (irradiation: 5 seconds and rest: 1 second). Skin and muscle temperatures were measured during both warm-ups. Skin and muscle temperatures increased significantly after 5 minutes of local muscle light exercise and after 10 minutes of polarized light irradiation. Temperatures were significantly higher after 6 minutes of local muscle light exercise than after 6 minutes of polarized light irradiation. There were no significant differences of muscle strength, power, and controlled force-exertion before and after either warm-up. Average force outputs in all conditions significantly decreased with exertion time, and at 30, 60, 90, and 120 seconds they were higher in both warm-up conditions than in the non-warm-up condition. In conclusion, both warm-ups may contribute to improve muscle endurance performance in the decreasing force phase.

View full abstract

The present study evaluated the effects of exposure to light intensity in the morning on dim light melatonin onset (DLMO). The tested light intensities were 750 lux, 150 lux, 3000 lux, 6000 lux and 12,000 lux (horizontal illuminance at cornea), using commercial 5000 K fluorescent lamps. Eleven healthy males aged 21–31 participated in 2-day experiments for each light condition. On the first experimental day (day 1), subjects were exposed to dim light (<30 lux) for 3 h in the morning (09:00–12:00). On the same day, saliva samples were taken in dim light (<30 lux) every 30 min from 21:00 to 01:00 to determine the DLMO phase. The subjects were allowed to sleep from 01:00 to 08:00. On the second experimental day (day 2), the subjects were exposed to experimental light conditions for 3 h in the morning. The experimental schedule after light exposure was the same as on day 1. On comparing day 2 with day 1, significant phase advances of DLMO were obtained at 3000 lux, 6000 lux and 12,000 lux. These findings indicate that exposure to a necessary intensity from an ordinary light source, such as a fluorescent lamp, in the morning within one day affects melatonin secretion.

View full abstract

The purpose of this study was to formulate a “sleep/wake” scoring algorithm for processing activity measurements obtained using a newly developed nonwear actigraphy (NWA) device, and to test its validity. The NWA device has a highly sensitive pressure sensor and is placed under a mattress. It can continuously record the activity of a person lying on the mattress and identify an “in-bed/out-of-bed” state from the vibrations of the mattress. We formulated the sleep/wake scoring algorithm by using data obtained simultaneously by wrist actigraphy (Act) and the NWA device in 33 healthy participants. Agreement rate, sensitivity, and specificity with Act were 95.7%, 97.6%, and 75.8% (33 healthy people); the corresponding values were 85.9%, 89.1%, and 79.8% for 12 nursing home residents and 93.7%, 97.2%, and 60.8% for 60 nights for 6 healthy persons who slept 10 nights on their futons. Agreement rate, sensitivity, and specificity with polysomnography were in almost perfect agreement with Act (12 nights; 6 healthy persons who slept 2 nights). All our validation results indicate that the NWA device, placed under a mattress or a futon, can produce almost identical sleep/wake scores to Act. It is expected that the NWA device, a nonwear device for scoring sleep/wake and in-bed/out-of-bed, enables convenient long-term sleep-related evaluation in various fields, including hospital settings, home-care settings, and care facility settings such as nursing homes.

View full abstract

This study aimed to clarify the regularity of leptin in Naqu Tibetan adolescents. This study investigated the concentration of fasting serum leptin and clarified its relationship between BMI and other indices. Healthy Naqu Tibetan adolescents aged 12–18 were investigated randomly in the study. They were divided into seven groups (each year as one group, 12 boys and 12 girls in each group); serum concentrations of leptin, estradiol, testosterone (T), follicle stimulating hormone (FSH) and luteinizing hormone (LH) were analyzed. The height and body weight of the 168 healthy Naqu Tibetan adolescents were also assessed. The leptin level in boys decreased with age but increased in girls; in boys and girls they both differed between groups (p<0.05). In boys, the leptin level was inversely correlated with body mass index (BMI), FSH, and T (p<0.05), while in girls, it was positively related to BMI, FSH, LH, and E₂ (p<0.01).These findings suggested that during puberty the serum leptin concentration increased with age in girls while it decreased in boys; in the same age group, the leptin level in girls was significantly higher than in boys. Leptin may have some relationship with puberty in Tibetan adolescents.

View full abstract

This study evaluated the accuracy of assessing step counts and energy costs under walking conditions altered by step frequency changes at given speeds using uni- (LC) and tri-axial accelerometers (AM, ASP). Healthy young men and women (n=18) volunteered as subjects. Nine tests were designed to manipulate three step frequencies, low (−15% of normal), normal, and high (+15%), at each walking speed (55, 75, and 95 m/min). A facemask connected to a Douglas bag was attached to subjects, who wore accelerometers around their waist. LC underestimated the step counts at normal or high step frequency at 55 m/min and AM also at all step frequencies at 55 m/min, whereas ASP did not in all trials. LC underestimated metabolic equivalents (METs) at low or normal step frequency at all walking speeds. AM underestimated METs at low step frequency at all walking speeds and at high step frequency of 95 m/min. ASP gave underestimates only at low step frequency of 95 m/min. The degree of the percentage error of METs for AM and ASP was affected by step frequency. Significant interaction between step frequency and speed was found that for LC. These results suggest that LC and AM can cause errors in step-count functions at a low walking speed. Furthermore, LC may show low accuracy of the METs measurement during walking altered according to step frequency and speed, whereas AM and ASP, which are tri-axial accelerometers, are more accurate but the degree of the percentage error is affected by step frequency.

View full abstract